Hot-water heating system



June 28, 1966 A. KURZ ETAL HOT-WATER HEATING SYSTEM 4 Sheets-Sheet lFiled Ju'ly 31. 1964 P pwz www www Z l Wad f. mkv

June 28, 1966 A. KURZ ETAL 3,258,203

HOT-WATER HEATING SYSTEM Filed July 51, 1964 4 Sheets-Sheet 2 June 28,1966 A. KURZ ETAL 3,258,203

HOT-WATER HEATING SYSTEM Filed July 51, 1964 4 Sheets-Sheet 5 June 28,1966 A. KURZ ETAL HOT-WATER HEATING SYSTEM Filed July s1. 1964 FVG. 6

4 Sheets-Sheet 4.

United States Patent O 3,258,203 HOT-WATER HEATING SYSTEM Adolf Kurz andHeinz van Lier, Wernau, Germany, assignors to `lunkers & Co. G.m.b.H.,Wernau, Germany Filed July 31, 1964, Ser. N0. 386,625 Claims priority,application Germany, Aug. 1, 1963, J 24,173 17 Claims. (Cl. 237-8) rIhepresent invention relates to lcentral heating systems in gener-al, andmore particularly to an improved hotwater heating system. Still moreparticularly, the invention relates to improvements in hot-water heatingsystems which operate on the principle of forced circulation created bya motor-driven circulating pump controlled by outside thermostats orroom fthermostats.

In many presently known hot-water heating systems wherein the source ofhea-t comprises a gasJheated heat exchanger, the heat exchanger normallycomprises one or more packages of laminations or fins which surround alength of the water containing coil and are heated by flames or gaseousproducts of combusti-on produced by a gas burner. A serious drawback ofsuch hot-Water heating systems is that the spaces between the ns of theheat exchanger :become clogged after short periods of use to therebyreduce the efficiency of the heat exchanger. The reason for clogging ofthe heat exchanger is that such hot-water heating systems normallycomprise a motordriven circulating pump ywhich operates intermittentlyin response to impulses received from a room thermostat or from anotherstarting device to cause circulation of water through the coil. When thepump is started, it begins to circulate a stream of cold water, orcomparatively cold water, which ows through the heat exchanger. Sincethe rate at which the water is circulated in response to operation ofthe pump is determined in advance, the quantity of water flowing throughthe heat exchanger is constant and the latter transmits to such water `acertain quantity of heat energy. Consequently, the heating effect is lowwhen the circulating pump is started, which means that the exposedsurfaces of the fins are coated with a layer of condensate which isdrawn from the surrounding -air and promotes the clogging of spacesbetween the adjoining fins.

In order to reduce such deposition of condensate, it was alreadyproposed to return a certain quantity of freshly heated water into aportion of the coil immediately upstream of the heat exchanger so thathot water blends with colder water and the heat exchanger receives apreheated mixture rather than a stream of cold or comparatively coldliquid. Such blending -is continued until the water temperature in theentire coil rises to a predetermined value at which no furtherprecipitation of condensate takes place or at which the deposition ofcondensate is negligible. Of course, the apparatus for effecting suchmixing of hot and cold water contributes greatly to the bulk, initialcost and maintenance cost of the hotwater heating system. In addition,such blending `apparatus normally comprises complicated control deviceswhich are prone to malfunction and must lbe serviced by highly skilledpersons.

Therefore, it was already proposed to replace such blending apparatus bythe provision of a main heater Iand an auxiliary heater which latter isused -to prevent the water temperature from descending below apredetermined value, i.e., the -auxiliary heater insures that the watertemperature remains ybetween a predetermined minimum value land apredetermined maximum value. Of course, this means that -the hot-waterheating system must comprise two heaters, two burners and acorrespondingly Patented June 28, 1966 ICB kincreased number of valves,piping, control elements and other accessories which Vadd to the bulk,cost and complicatedness of the assembly.

Accordingly, it is an important object of the present invention toprovide a very simple, reliable and compact -hot-water heating systemwhich avoids the drawbacks of conventional heating systems and whereinthe deposition of condensate on the fins of the heat exchanger iseliminated in a novel way.

Another object of the invention is to provide a hotwater heating systemwhose operation is automatic and wherein a small number of comparativelysimple auxiliaries suliices to prevent clogging of spaces between thefins of the heat exchanger.

A further object of the invention is to provide `a hotwater heatingsystem wherein the heating of the heat exchanger produces little noiseand wherein the admission of -fuel to the burner or burners may takeplace in a fully automatic way and at low water pressure.

With the above objects in view, one feature of ou present inventionresides in the provision of a hot-water heating system which comprises acoil defining an endless path for a supply of water, a pump whichcirculates water in :the coil, a =burner for heating the water whichcirculates in the coil, a normally closed regulating valve provided in acon-duit which supplies gas or yanother fuel to the burner, means forproducing a pressure dilferential in two spaced portions of the coilwhen the pump operates to circulate the water, a safety devicecomprising a pair of water-iilled chambers each communicating with oneof the two spaced portions of the coil so that the water pressure in oneof the chambers exceeds the Water pressure in the other chamber,actuating means operatively connected with the regulating valve toinitiate :the admission of fuel to the burner in response to apredetermined pressure differential in the chambers, and a throttlingdevice comprising a thermostat valve which is mounted in the coilupstream of the point where the other chamber communi-V cates with thecoil. This thermostat valve serves to throttle the flow of water atleast at such times when the waiter temperature in the coil is below apredetermined va ue.

The burner heats the tins of a heat exchanger which is provided along lalength of the coil, and the throttling action of the 4thermostat valveis suchthat the spaces between the tins cannot accumulate condensate4from surrounding air because the flow of water is throttled Suthcientlyto insure rap-id heating of water in the heat eX- changer to atemperature which is so high that the exchange of heat between the nsand water'does not result in cooling of fins to a temperature at whichthe deposition of condensate can take place.

The novel features which are considered as characlteristic of theinvention are set forth in particular in the appended claims. Theimproved heating system itself, however, yboth as to its constructionand its modeI of operation, together with additional features andadvantages thereof, will be best understood upon perusalof the followingdetailed description of certain specific embodirnents with reference tothe accompanying drawings, in which:

FIG. 1 is a somewhat schematic view of a forcedc1rculation hot-waterheating system which is constructed in accordance with a firstembodiment of the present invention, certain portions of the heatingsystem being shown in section;

FIG. 2 is -a central vertical sec-tion through la throttling devicewhich is utilized in the heating system of FIG.` 1;

FIG. 3 i-s a horizontal section as seen in the direction of arrows fromthe line IV-lV of FIG. 2;

FIG. 4 is a Vertical section through the thermostat valve of thethrottling device a-s seen in the direction of arrows from line 1V-IV ofFIG. 2;

FIG. 5 is a schematic view of a modified hot-waterheating system; 1andFIG. 6 is a similar schematic view of a third hot-water heating system.

Referring to FIG. 1, there is shown a hot-Water heating system includinga coil 11, 12 which defines a closed path fora supply of water, acirculating pump 14, a heat exchanger 15 having -fins 15a surrounding alength of the coil, a gas burner 16 which is located beneath and heatsthe fins 15a, `and heat dissipating elements in the form of radiators10,v only one such radiator being actually shown in the drawing. Theradiator 10 is installed downstream of the heat exchanger but upstreamof the pump 14. The flow of fuel to the burner 16 is controlled by asafety device 19 which is responsive to a pressure differential betweenthe interior of the clod-water (return) section 12 and the hot-watersection 11 of the coil. Upstream of the pump 14, the return section 12communicates with an expansion line 13 leading to an expansion tank 13a.

The flow of fuel to the burner 16 is controlled by a normally closedregulating valve 17 which is mounted in a supply conduit 18. Thisregulating valve 17 is a gas valve of known design and is operated bythe safety device 19 which comprises a casing accommodating an actuatingelement here shown as a deformable diaphragm 20 so as to divide itsinterior into `chambers 21, 22. The diaphragm 20 is connected with andserves as a means for moving the valve member 17a of the valve 17 awayfrom its seat 17b. The valve member 17a is biased by a spring 17C. Thechamber 21 is connected with the return section 12 by a high-pressurepipe 23 which communicates with the section 12 at the downstream side ofthe pump 14, and the chamber 22 is connected with a low-pressure pipe 24leading to the hot-water section 11. The chamber 21 is the high-pressurechamber and the chamber 22 is the low-pressure chamber. When the pump 14is started, the heat exchanger 15 offers a certain resistance to theflow of water through the coil so that pressure prevailing in thechamber 21 exceeds th-e pressure in the chamber 22. The pressuredifferential causes the diaphragm 20 to move `the valve member 17a awayfrom the seat 17b and to admit gaseous fuel from the supply conduit 18into the burner 16. Such fuel is ignited by an automatic igniter device-of any known design, not shown in the drawings.

In -accordance with the presen-t invention, the rate at which Water maycirculate through the coil is controlled by a throttling device 25 whichis installed in the hotwater section close to and upstream of the pointwhere this section communicates with the low-pressure pipe 24. Thethrottling device 25 is operative when the valve 17 admits fuel to theburner 16 and when the water temperature in the coil is below apredetermined value. The device 25 lthen insures that the flow of waterthrough the hot-water section 11 is throttled whereby the burner 16heats a small quantity of water per unit of time. The throttling actionof the device 25 is proportional to the temperature of water anddecreases in response to rising water temperature. When the entiresupply of water in the coil 11, 12 is heated to a predeterminedtemperature, the throttling device 25 is fully opened and allows formaximum (normal) circulation of water. In accordance with a preferredembodiment of our invention, the throttling device 25 comprises athermostat valve which regulates the cross-sectional area of the passagein the hot-Water section 11. `-It will be noted that Ithe device 25 isinstalled upstream of the point Where the chamber 22 communicates withthe section 11 of the coil and upstream of the point where the chamber22 communicates with the pipe 24.

FIGS. 2 to 4 illustrate the construction of throttling device 25. Thisdevice comprises a housing 30 including two open-ended tubular portions31, 32. The open lower end of the upper portion 31 is connected to theopen upper end of the lower portion 32 by a joint 33 which is llocatedin a horizontal plane and supports a thermostat valve 34. The valve 34comprises an annular valve member 36 which is biased by a resilientelement here shown as a helical spring 35. The periphery of the valvemember 36 is adjacent to an annular valve seat 38 having an annularflange 37 which is clamped between the tubular portions 31, 32. When thewater temperature in the hot-water section 11 of the coil descends to orbelow a predetermined minimum value, the spring maintains the valvemember 36 in the axial position of FIG. 4 so that the valve member 36and the seat 38 define between themselves an annular gap 39 which allowsa minimum quantity of water to flow from the heat exchanger 15 to theradiator 10. The fiange 37 is conneet-ed with a lower carrier or yoke 40and with an upper carrier or yoke 41. These yokes partially enclose thevalve member 36 and the yoke 40 carries an upwardly extending projectionor pin 42 secured thereto by a nut 42a. The pin 42 is slidable in anaperture provided in the bottom wall of a jacket here shown as acylinder 43, and this cylinder is formed with a circumferential shoulder44 `for Ithe valve member 36. The upper end portion of the cylinder 43extends through 4and beyond an aperture provided in the median portionof the yoke 41, and the internal space of the cylinder accommodates anannular sealing member 45 which is adjacent to the apertured bottom walland forms a fluid-tight seal around the pin 42. The upper por-tion ofthe internal space in the cylinder 43 is filled with a material 46 whichexpands in response to a rise in temperature Iof the cylinder such as isbrought about by changes in the temperature of water which flows in thehot-water section 11. The upper leg 11a of this hot-water section isconnected to the cylindrical wall of the upper tubular portion 31 andthe lower leg of the section 11 comprises a nipple 11b which i-s securedto the bottom wall `of the lower tubular portion 32 so that waterflowing through and beyond the heat exchanger 15 may enter the upperportion 31 to flow around the cylinder 43, through the gap 39, throughthe lower portion 32 and into the nipple 11b.

The material 46 has a predetermined coefficient of expansion and allowsthe valve member 36 to remain in the lower end position of FIG. 4 whenthe Water tempera-ture in the section 11 reaches or descends below apredetermined minimum value. The valve member,36 is then held in suchlower end position by the spring 35 which forces the pin 42 to penetrateinto the material 46 by operating between the upper yoke 41 and thevalve member, i.e., between the yoke 41 and the shoulder 44 of thecylinder 43. The latter is slidable in the centrally located aperture ofthe yoke 41.

When the temperature -of water flowing through the section 11 begins torise, the material 46 expands gradually and expels a portion of the pin42 from the internal space Iof the cylinder 43 whereby the cylinderbegins to move upwardly, as viewed in FIG. 4, and the cross-sectionalarea of the gap 39 between the valve member 36 and valve seat 38increases proportionally so that the water may circulate at a higherrate. The expansion coefficient of the material 46 is such that Ithebias of the spring 35 is overcome only at the time the temperature ofwater flowing in the section 11 rises above a predetermined minimumvalue. Also, in the initial stage of expansion of the material 46, thecross-sectional area of the gap 39 preferably remains unchanged orincreases very little (see FIG. 6 which shows that the peripheralportion of the valve member consists of a short cylinder which issurrounded by a concentric cylindrical portion of the valve seat 38 sothat the cross-sectional area of the gap 39 remains unchanged as long asthe cylindrical portion of the valve member 36 is actually surrounded bythe cylindrical portion of the valve seat). In other words, 4thecross-sectional area of the gap 39 begins to increase gradually when thetemperature of w-ater in the section 11 rises to a value which isnecessary to bring about a predetermined compression (shortening) of thespring 35 so that the cylindrical portion of the valve member 36 risesto a level above Ithe cylindrical portion of the valve seat 38.

It will be seen that the 4throttling device 25 allows for circulation ofa smaller quantity of water when the water temperature is below apreselected value whereby the water filling that length of the coilwhich is surrounded by the Iins a of the heat exchanger 15 remains inlongerlasting heat-exchanging contact with the tins 15a and is rapidlyheated to a temperature at which the device responds to allow forincreased circulation of water through the coil. The thermostat valve 34causes the throttling device 25 to open fully at the time the watertemperature reaches or rises above a predetermined maximum value.

It is a rather simple procedure to selec-t the minimum cross-sectionalarea of the gap 39 and the material 46 in such a way that watercirculating in the coil 11, 12 may be heated without causing any (or bycausing negligible) deposition of condensate on the fins 15a. As a rule,the valve member 36 will be biased to the position of FIG. 6 wheneverthey flow of gaseous fuel to the burner 16 is shut off and whenever thewater temperature drops below a predetermined minimum value so that theabovedescribed operation begins as soon `as -the valve 17 admit-s fuelt-o the burner 16 4and the latter begins to heat the ns 15a.

FIG. 5 illustrates a somewhat modified` hot-water heating system whereinthe high-pressure chamber 21 of the control device 19 is connected to ahigh-pressure pipe 223 leading to the hot-water section 11 at a pointupstream of the throttling device 25. The low-pressure pipe 24communicates with the throat portion of `a Venturi 26 which is providedin the sec-tion 11 downstream of the throttling device 25, i.e., theinlet of the Venturi receives water which has passed through the gap 39of the thermos-tat valve 34 in the housing 30 of the device 25. In FIG.5 the Venturi 26 produces the pressure differential which is necessaryto keep the gas valve 17 in open position.

It will be seen that the throttling device is again located upstream ofthe point where the chamber 22 communicates with -the pipe 24.

FIG. 6 illustrates a third hot-water heating system which differentiatesfrom the systems of FIGS. 4 and 5 in that the lhigh-pressure pipe 323connects the chamber 21 with the section 11 at a point downstream of thepoint where the pipe 24 communicates with this section 11. The pres-lsure differential necessary to operate the control device 19 is producedmainly by a Venturi 326 which is provided in the section 11 and whosethroat portion communicates with the intake end of the pipe 24. Amodified throttling device 27 is located upstream of the Venturi 326 andcooperates therewith to regulate'the flow of water through the section11. This throttlingdevice 27 comprises a thermostat which controls theaxial position of a needle-shaped valve member 27a extending into andeyond the inlet of the Venturi 326. Changes in axial position of thevalve member 27a will bring about changes in the cross-sectional area ofthe annular orifice in the Venturi 326 so that the rate of water How maybe regulated in .a manner analog-ous to that described in connectionwith FIGS. l to 4. The thermostat which regulates the axial position ofthe valve member 27a comprises Va sensing element 27b which is incontact with water owing toward the Venturi 326.

Otherwise, the construction of the systems shown in 6 FIGS. 5 and 6corresponds exactly to that of the system shown in FIG. 1.

It will be readily understood that, even though the drawings illustratehot-water heating systems whose burners operate with gaseous fuel, suchburners may be replaced by other types of burners which utilize liquidor solid fuel. Also, while the drawings show heating systems wherein theregulating valve 17 is controlled by a safety device 19 which opens thevalve 17 in response to a differential in water pressure, this safetydevice 19 may be replaced by other types of safety devices, for example,by a magnetic valve which regulates the admission of fuel in response toimpulses furnished by a thermostat or in response to operation of thecirculating pump 14. All that counts is to provide a thermostatic-allyregulated throttling device which controls the rate of water circulationin such a way that the rate of flow depends on the temperature of waterso as to prevent the deposition of condensate on the heat exchangerwhereby the spaces between the fins 15 remain free and allow for eicientexchange of heat between the fins and the products of combustion orllames of the burner 16. This is due to the fact that small quantitiesof water which circulate through the heat exchanger 15 when thethrottling device reduces the rate of flow undergo a very intensiveheating action and the water temperature rises rapidly. Consequently,the fins 15a are maintained at a temperature which is high enough toprevent deposition of condensate. As soon as the deposition ofcondensate is prevented, there is no danger that the spaces between theiins 15a would become clogged.

FIGS. l, 5 and 6 show that, when the hot-water heating system comprisesa safety device 19, the throttling device 25 or 27 is preferablypositioned in that section of the coil in which the pressuredifferential exists, i.e., in the hot-water section 11, whereby thethrottling device may be installed upstream of the low-pressure pipe 24but downstream of the high-pressure pipe 23 or 223 (FIGS. l and 5) orupstream of the pipes 24, 323 (FIG. 6). In FIG. l, the pressuredifferential is produced solely by the Vresistance to water flow whichis offered by the heat exchanger 15. In FIG. 5, such pressuredifferential is produced mainly by the Venturi 26, and in FIG. 6 ghepressure differential is produced mainly by the Venturi Another veryimportant advantage of our hot-water heating system is that the systemis practically'noiseless which is attributable to the fact that thethrottling device 25 or 27 allows water to circulate at a rate whichincreases in proportion to rising water temperature. In manyconventional hot-water heating systems, water which is overheated in theheat exchanger will produce a hissing sound which is unpleasant to humanears.

Furthermore, the throttling device 25 or 27 insures that the resistanceto ow is rather high when the water temperature is low whereby the gasvalve 17 may open in response to low water pressure and remains openwhen the resistance which the throttling device olfers to ow of waterdecreases at elevated temperatures. The throttling device is reliable inoperation and requires little attention. Also, by effecting certainminor adjustments ad system utilizing our improved throttling device maybe used with advantage in heating systems which operate with boilingwater.

The material 46r used in the cylinder 43 of the throttling device 25 maybe a wax like product.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecic aspects of this invention and, therefore, such adaptations shouldand are intended to he comprehended within the meaning and range ofequivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a hot-water heating system, in combination, a coil defining anendless path for a supply of water; pump means for circulating the waterin said coil; .a burner arranged to heat the water in said coil; aconduit for suppling fuel to said burner; a normally closed regulatingvalve provided in said conduit; means for producing a pressu-redifferential in two spaced portions of said coil when the water iscirculated by said pum-p means; a safety device comprising a pair ofwater-filled chambers each communicating with one of said spacedportions of the coil so that the water pressure in one of said chambersexceeds the water pressure in the other chamber, and actuating meansoperatively connected with and arranged to open said regulating valve inresponse to such pressure differential in said chambers; and athrottling device comprising a thermostat Valve mounted in said coilupstream ofthe point where said other chamber communicates with thecorresponding portion of said coil and arranged to throttle the ow ofwater at least when the water temperature in said coil is below apredetermined value.

2. In a hot-water heating system, in combination, a coil defining anendless path for a supply of water; pump means for circulating the waterin said coil; a burner arranged to heat the water -in said coil; aconduit for supplying fuel to said burner; a normally closed regulatingvalve provided in said conduit; means for producing a pressure`differential in two spaced portions of said coil when the water iscirculated by said pump means; a safety de-vice comprising a pair ofwater-filled chambers eac-h communicating with one of said spacedportions of the coil so that the water pressure in one of said chambersexceeds the water pressure in the other chamber, and actuating meansoperatively connected with and arranged to open said regulating valve inresponse to such pressure differential in said chambers; and athrottling device comprising a thermostat valve mounted in said coilbetween said spaced portions thereof and arranged to throttle the ow ofwater at least lwhen the weiter temperature in said coil is below apredetermined va ue.

3. A structure as set forth in claim 2, wherein that one of said spacedportions which communicates with said other chamber is locateddownstream of the other spaced portion.

v74. In a hot-water heating system, in combination, a coil defining anendless path for a supply of water; pump means for circulating the waterin said coil; a burner arranged to heat the water in said coil; aconduit for supp-lying fuel to said burner; a normally closed regulatingvalve provided in said conduit; means including a Venturi for producinga pressure differential in two spaced portions of said coil when thewater is circulated by said pump means whereby .the portion containingwater whose pressure is higher is located upstream of said Venturi; asafety device comprising a pair of water-filled chambers eachcommunicating with one of said spaced portions of the coil so that thewater pressure in that one of said chambers which is connected with theportion located upstream of said Venturi exceeds the water pressure inthe other chamber, and actuating means operatively connected with andarranged to open said regulating valve in response to such pressuredifferential in said chambers; and a throttling device comprising athermostat valve mounted in .said coil upstream of said Venturi anddownstream of the portion containing water whose pressure is higher,said thermostat valve being arranged to throttle `the flow of water vatleast when the water temperature in said coil is below a predeterminedvalue.

5. A structure as set forth in claim 4, wherein said Venturi comprises athroat portion and wherein said other chamber communicates with saidthroat portion.

6. In a hot-water heating system, in combination, a coil defining anendless path for a supply of water; pump means for circulating the waterin said coil; a burner arranged to heat the water .in said coil; aconduit for supplying fuel to said burner; a normally closed regulatingvalve provided in said conduit; means including a Venturi for producingla pressure differential in two spaced portions of said coil when thewater is circulated by said pump means whereby the portion lcontainingwater whose pressure is higher is located downstream of the otherportion and downstream of said Venturi; a safety device comprising apair of water-filled chambers each communicating with one of said spacedportionsof'the coil whereby the water pressure in that one of saidchambers which is connected with the portion containing water whosepressure is higher exceeds the Water pressure in the other chamber, andactuating means operatively connected with and arranged to open saidregul-ating valve in response to such pressure differential in saidchambers; and a throttling device comprising a thermostat valve mountedin said coil upstream of said Venturi, said thermostat valve having areciprocable valve member adjacent to said Venturi and atemperature-responsive sensing element pro-vided in said coil andoperatively connected ywith said valve member to reciprocate the latterin response to changes in water temperature so that said Valve memberthrottle-s the flow of water through said Venturi at least when thewater temperature in said coil is -below a predetermined value.

7. A .structure as set lforth in claim 6, wherein said valve member is aneedle which extends through the inlet of said Venturi.

8. A structure as set forth in claim 6, wherein said Venturi comprises a.throat portion and the `other chamber communicates with said throatportion.

9. In a hot-water heating system, in combination, a coil defining anendless path yfor a supply of water; pump means yfor circulating thewater in said coil; a burner arranged to heat the water in said coil; aconduit for supplying fuel to said burner; a normally closed regulatingvalve provided in said conduit; means for producing a pressuredifferential in two spaced portions of said coil when the water iscirculated by said pump means; a safety device comprising a pair ofwater-filled chambers each communicating with one of said spacedportions of the coil so that the water pressure in one of said chambersexceeds the water pressure in the other chamber, and actuating meansoperatively connected with and lar-ranged to open said regulating valvein response to such pressure differential in said chambers; and athrottling device comprising a housing having two tubular housingportions connected in said coil upstream of the point where said otherchamber communicates with the corresponding portion of said coil so thatthe circulating water flows through said housing portions, said housingportions having open ends adjacent to each other, a joint sealinglyconnecting said open ends with each other, and a thermoi stat valveprovided in said lhousing and including an annular seat secured to saidjoint, a valve member reciprocable in and defining with -said seat -anannular gap of variable cross-sectional area, and means responsive towater temperat-ure in said housing and operatively connected with I-saidvalve member to reciprocate :the valve member with reference to saidseat and to increase the cross-sectional area of sa-id gap when `thewater temperature in said yhousing rises above a predetermined value.

'10. A structure as set forth in claim 9, wherein said thermostat valveyfu-rther comprises resilient mean-s for biasing said valve member to aposition in which the cross-sectional area of said gap is reduced -to aminimum when the water temperature drops to said predetermined value.

il. In a hot-water heating system, in combination, a coil defining anendless path for a supply of water; pump means for circulating the waterin said coil; a heat exchanger having fins exposed to a humiditycontaining atmosphere, said tins surrounding a length of the coildownstream of .said pump means; a burner arranged to heat said nswhereby the heat exchanger 'heats the water in said coil Iand said iinsexhibit a tendency to collect conde-nsate from the surrounding -humiditycontaining atmosphere -when the water temperature in said length of coilis below a predetermined value; heat-dissipating means provided in saidcoil downstream of said heat exchanger but upstream of said pump means;a throttling v-alve for regulating the rate of water flow through saidcoil, said throttling valve provided in said coil adjacent to anddownstream of said heat exchanger but upstream of said heat dissipatingmeans; and thermostatic actuating means dependent upon the watertemperature in the region of said throttling valve adjacent to anddownstream of said heat exchanger -for reducing the rate of water flow,when the water temperature in the region of said ylength of the coildrops below said predetermined value below which condensate would tendto collect on said fins, so that the ow of water through said length ofco-il is slowed down whereby the water temperature in said length ofcoil rapidly rises above said predetermined value to at least reduce theaccumulation of condensate on said iins.

1'2. In a hot-water 'heating system, in combination, a coil defining anendless path for a supply of water; pump means lfor circulating thewater in said coil; a heat exchanger having tins exposed to a humiditycontaining atmosphere, said ins surrounding a length of the coildownstream of said pump means; a burner arranged to heat said ns wherebythe heat exchanger heats the water in said coil and said fin-s exhibit atendency to collect condensate from the surrounding humidity containingatmosphere when the water temperature in said length -of coil is below apre-determined value; a throttling Val-ve for regulating the rate ofwater ow through said coil, said throttling valve provided in said coiladjacent to and downstream of said heat exchanger but upstream of saidpump means; and thermostatic actuating means dependent upon the watertemperature in the region of said throttling valve adjacent to anddownstream of sai-d heat exchanger =for reducing the rate of huid flowwhen -the water temperature in the `region of said length of the coildrops below said predetermined value below which condensate would tendto collect on said iins, so that the tow of water through said length ofcoil is slowed down whereby the water temperature in said length of coilrapidly rises above said ipredetermined value to at least reduce theaccumulation of condensate on said ns.

13. In a hot-water heating system, in combination, a coil deiining anendless path `fora supply of water; pump means for circulating the waterin said coil; a heat exchanger having fins surrounding a length of thecoil downstream of said pump means; a burner arranged to heat said hnswhereby the heat exchanger heats the water in said coil and said nsexhibit a tendency to collect condensate lfrom the surrounding air whenthe water temperature in said coil is below a predetermined value; asupply conduit arranged to supply fuel to said burner; a normallyclose-d regulating valve provided in said supply conduit; a safetydevice for opening said regulating valve in response to circulation ofwater in said coil; and a throttling device for regulating the rate ofwater flow through said coil, said throttling device comprising athermostat Valve provided in said coil downstream of said heat exchangerbut upstream of said pump means and arrange-d to reduce the rate of uidflow, at least when the water temperature is below said 'predeterminedvalue, so that the water temperature in said length of coil rapidlyrises above said predetermined value to at least reduce the accumulationof condensate on said `tins.

14. A structure as set tforth in claim 13, wherein said safety device isresponsive to a pressure differential in two spaced portions of saidcoil and wherein such pressure differenti-al is produced at least inpart by the resistance offered by said heat exchanger to the circulationof water through said length of coil.

15. In a hot-water heating system, in combination, a coil dening anendless path `for a supply of water; pump means for circulating thewater in said coil; a heat exchanger having ns surrounding a length ofthe coil downstream of said pump means; a burner arranged to heat saidtins whereby the heat exchanger heats the water in said coil and saidIfins exhibit a tendency to collect condensate from the surrounding air[when the water temperature in said coil is below a predetermined value;heat-dissipating means provided in said coil downstream of said heatexchanger Ibut upstream ot said pump means; and a throttling device yforregulating the lrate of water flow through said coil, said throttlingdevice comprising a thermostat valve provided in said coil downstream ofsaid heat exchanger but upstream of said heat-dissipating means andarranged to reduce the rate of uid flow, at least when the watertemperature is below said predetermined value, so that the watertemperature in said length of coil rapidly rises above saidpredetermined value to at least reduce the accumulation of condensate onsaid fins, said thermostat valve comprising a Venturi provided in saidcoil and having an inlet, a valve member reciprocably extending throughthe inlet of said Venturi to thereby regulate the rate of water liowthrough the Venturi, and a temperature-responsive sensing elementpro-vided in said coil and operatively connected to said valve member toreduce the rate of water how through said Venturi when the 'watertemperature descends to said predetermined value.

16. In a heating system, in combination, a coil dening an endless pathfor a supply of fluid, a heat exchanger and at least one heatdissipating element provided in said coil; burner means arranged to heatsaid heat exchanger whereby the latter heats the fluid; means forcirculating the uid in said coil; conduit means connected with Iandarranged to supply fuel to said burner means; a normally closedregulating valve provided in said conduit means; a safety device foropening said regulating valve in response to a pressure differential intwo spaced portions of said coil; :and an adjustable throttling deviceAfor regulating the rate at which the fluid may circulate in said coil,said throttling device comprising a thermostat valve mounted in saidcoil and arranged to throttle the flow of duid at least when the huidtemperature in said coil remains below a predetermined value.

17. A struct-ure as set forth in claim `16, wherein said heat exchangercomprises at least one package of flins dening between themselves spaceswhich collect condensate from the surrounding air when the temperatureof `fluid in said coil drops to said predetermined value, saidthrottling device being arranged to prevent such accumulations ofcondensate in said spaces by throttling the ow of huid sutiiciently toinsure tha-t huid contained in said heat exchanger is rapidly heated toabove said predetermined temperature.

References Cited by the Examiner UNITED STATES PATENTS 1,061,635 5/1913Ross 237-8 2,194,805 3/ 1940 Moore 237-8 2,340,844 2/ 1944 -Dillman237-8 2,981,477 4/ 1961 Salmon 236-34 3,201,045 8/ 1965 Davidson et al237-8 FOREIGN PATENTS 1,201,596 7/1959 France.

EDWARD I. MICHAEL, Primary Examiner.

1. IN A HOT-WATER HEATING SYSTEM, IN COMBINATION, A COIL DEFINING ANENDLESS PATH FOR A SUPPLY OF WATER; PUMP MEANS FOR CIRCULATING THE WATERIN SAID COIL; A BURNER ARRANGED TO HEAT THE WATER IN SAID COIL; ACONDUIT FOR SUPPLING FUEL TO SAID BURNER; A NORMALLY CLOSED REGULATINGVALVE PROVIDED IN SAID CONDUIT; MEANS FOR PRODUCING A PRESSUREDIFFERENTIAL IN TWO SPACED PORTIONS OF SAID COIL WHEN THE WATER ISCIRCULATED BY SAID PUMP MEANS; A SAFETY DEVICE COMPRISING A PAIR OFWATER-FILLED CHAMBERS EACH COMMUNICATING WITH ONE ONE OF SAID SPACEDPORTIONS OF THE COIL SO THAT THE WATER PRESSURE IN ONE OF SAID CHAMBERSEXCEEDS THE WATER PRESSURE IN THE OTHER CHAMBER, AND ACTUATING MEANSOPERATIVELY CONNECTED WITH AND ARRANGED TO OPEN SAID REGULATING VALVE INRESPONSE TO SUCH PRESSURE DIFFERENTIAL IN SAID CHAMBERS; AND ATHROTTLING DEVICE COMPRISING A THERMOSTAT VALVE MOUNTED IN SAID COILUPSTREAM OF THE POINT WHERE SAID OTHER CHAMBER COMMUNICATES WITH THECORRESPONDING PORTION OF SAID COIL AND ARRANGED TO THROTTLE THE FLOW OFWATER AT LEAST WHEN THE WATER TEMPERATURE IN SAID COIL IS BELOW APREDETERMINED VALVE.